It's been quite awhile since I've been there but I like Dado tea in Cambridge. I noticed it is now called Dado Tea and Coffee though! I believe they specialize in Korean tea.
http://www.dadotea.com/page/Visit-Us.aspx

Am joining the conversation pretty late, I know, but just want to say that I'm glad I came across this thread. Like Katrina, I am baffled by the dearth of good tea shops and tea rooms in Boston. I will check out TeaZone, and the Kaji Aso studio. As for Dado, it's a solid bet, but its atmosphere isn't all that different from that of the Starbucks across the street (i.e., lots of students on their laptops, and it's often pretty busy). One final suggestion: if you're looking for Mariage Freres tea, Louis Boston has a good selection. I bought some decent Darjeeling there recently.

I've been trying to visit Kaji Aso for 3 weeks now but it seems it might take a while. First the person responsible for the ceremony was away, then it was available just for groups and for the past two calls i gave my contact info and still waiting.
I dont know much about japanese culture but i guess patience is a must have requirement. Still trying to go to to teazone but been too busy to drive there. anyway i got so much tea at home that its almost insane to go out for more tea!!!!